Earthworms Reduce Biotic 15-Nitrogen Retention in Northern Hardwood Forests

    Authors

    H. A. Ewing; A. R. Tuininga; P. M. Groffman; K. C. Weathers; T. J. Fahey; M. C. Fisk; P. J. Bohlen;E. Suarez

    Comments

    Authors: contact us about adding a copy of your work at STARS@ucf.edu

    Abbreviated Journal Title

    Ecosystems

    Keywords

    ammonium; earthworms; hardwood forest; hydrology; invasive species; nitrate; nitrogen retention; nutrient cycling; microbes; soils; SOIL ORGANIC-MATTER; NORTHEASTERN UNITED-STATES; TEMPERATE FORESTS; LUMBRICUS-TERRESTRIS; MICROBIAL BIOMASS; EXOTIC EARTHWORMS; NEW-YORK; DECIDUOUS FOREST; NITROGEN; INVASION; Ecology

    Abstract

    Invasive exotic earthworms are significantly influencing understory community composition, soil, and ecosystem processes in northern hardwood forests in North America, but their effect on the retention of nitrogen (N) has been inconclusive. We examined this in two northern hardwood forest sites in New York state, USA through a tracer study. In both spring and fall, we added tracer amounts of N-15 as nitrate-to simulate atmospheric deposition-with the biologically less active tracer bromide (Br-) to areas both with and without large populations of invasive earthworms. Total recovery of N-15 was lower in earthworm-invaded plots, largely due to less retention in litter and upper soil horizons. Although the strong relationship between retention in the upper soil horizons and total N-15 recovery suggests that earthworm destruction of the forest floor may be one mechanism reducing the capacity for N retention, in some cases the mineral soil in earthworm-invaded plots retained substantial N. Biotic pools, particularly litter and microbial biomass, retained significantly less N-15 in earthworm-invaded plots than in their uninvaded counterparts. In plots invaded by earthworms, negative effects of earthworms on trees were revealed through root-uptake assays suggesting somewhat greater plant demand for ammonium in the spring and in lower N-15 recovery in maple seedlings the year following tracer addition. Although similar patterns of Br- movement across treatments suggested that earthworms had smaller effects on hydrologic tracer movement than expected, they appear to have significant effects on the biological processes that underlie N retention.

    Journal Title

    Ecosystems

    Volume

    18

    Issue/Number

    2

    Publication Date

    1-1-2015

    Document Type

    Article

    Language

    English

    First Page

    328

    Last Page

    342

    WOS Identifier

    WOS:000350880400011

    ISSN

    1432-9840

    Share

    COinS